Add OAUTH support for Mail for GSuite users

If you use GSuite from Google for outgoing mail in WHMCS Google will no longer support mail connections from WHMCS with a username and password only starting on February 15, 2021.

Access through only a username and password makes your account more vulnerable to hijacking attempts. Moving forward, only apps that support a more modern and secure access method called OAuth will be able to access your G Suite account.

To continue using a specific app with your G Suite accounts, users in your organization must switch to a more secure type of access called OAuth. This connection method allows apps to access accounts with a digital key instead of requiring a user to reveal their username and password. We recommend that you share the user instructions (included below) with individuals in your organization to help them make the necessary changes. Alternatively, if your organization is using custom tools, you can ask the developer of the tool to update it to use OAuth. Developer instructions are also included below.

Access to LSAs will be turned off in two stages:

June 15, 2020 - Users who try to connect to an LSA for the first time will no longer be able to do so. This includes third-party apps that allow password-only access to Google calendars, contacts, and email via protocols such as CalDAV, CardDAV and IMAP. Users who have connected to LSAs prior to this date will be able to continue using them until usage of all LSAs is turned off.

February 15, 2021 - Access to LSAs will be turned off for all G Suite accounts.

if WHMCS is considering adding in OAuth for Gmail/GSuite email, how about take it a step further and add in a "GSuite Server" module? using WHMCS for onboarding new clients has been a challenge, where only third party modules/addons can truly accomplish the task correctly.

BUT... the prolonging issue that i face with my clients is the "GSuite Management" from the client end. it *really is* SO much easier to use the native Add User function in GSuite, that most of my GSuite clients find it really complicated going through the process of adding/removing seats through the WHMCS interface. *Anything* that WHMCS developers could do to simplify that process would be a dream come true!!!